Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are persistent, bioaccumulative and toxic pollutants found in the environment. The Passaic River in New Jersey is highly contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TeCDD), one of the most toxic of the PCDD/F congeners. Our on-going research at Rutgers is intended to better understand PCDD/F dichlorination by anaerobic organohalide respiring bacteria (OHRB). Results will be presented from various anaerobic enrichment cultures (including from the Passaic River) enriched on alternate organohalides such as trichloroethene and dichlorobenzene to stimulate OHRB. Activity against three PCDD congeners: 1,2,3,4-tetrachlorodibenzo-p-dioxin, a well-studied model PCDD congener; 2,3,7,8-TeCDD; and 2,7-dichlorodibenzo-p-dioxin, a potential metabolite of 2,3,7,8- TeCDD, have been investigated. After 1.5 years, dechlorination of all tested dioxin congeners was observed in one or more replicate of each Passaic River sediment treatment. Preliminary 16S rRNA gene sequencing indicates dominance of a specific Dehalococcoidia phylotype in the 2,3,7,8-TeCDD dechlorinating enrichment. Further characterization of the bacteria could provide methods for monitoring dechlorination in contaminated sites and lead to new in situ treatment technologies